The semiconductor integrated circuit (IC) industry has experienced exponential growth. Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs. Such scaling down has also increased the complexity of processing and manufacturing ICs and, for these advancements to be realized, similar developments in IC processing and manufacturing are needed.
For example, multi-gate devices have been introduced in an effort to improve gate control by increasing gate-channel coupling, reduce OFF-state current, and reduce short-channel effects (SCEs). One type of multi-gate devices is FinFETs—transistors with a fin-like semiconductor channel (“fin”) and a gate electrode engaging the fin on two or three sides thereof. A further advancement in FinFET is the replacement of the typically poly silicon gate electrode with a metal gate electrode to improve device performance. This is termed a “replacement gate” or “gate last” process in which a dummy gate (e.g., a poly silicon gate) is fabricated over the fin and is replaced with a final gate stack (e.g., a metal gate) in later fabrication steps. This allows for reduced number of subsequent processes, including high temperature processing, that is performed after the formation of the final gate stack. However, there are challenges to implementing such IC fabrication processes, especially with scaled down IC features in advanced process nodes. One challenge is that after the fin is formed and before the dummy gate is formed, the fin may suffer from buckling and collapsing during cleaning and drying processes due to its high aspect ratio (a ratio of fin height over fin width).